Fire check



vNov. 17, 1959 J. R. WILLIAMS 2,913,320

FIRE CHECK I Filed Sept. 7, 1956 2 Sheets-Sheet 1 INVENTOR. JOHN ROGERWILLIAMS ATTORN EY.

J. R. WILLIAMS FIRE CHECK Nov. 17, 1959 2 Sheets-Sheet 2 Filed Sept 7,1956 FIG. 2

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INVENTOR. JQI'IN ROGER WILLIAMS ATTORNEY.

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FIRE CHECK Application September 7, 1956, Serial No. 608,564

6 Claims. (Cl. 48192) The present invention relates to safety apparatus,and more particularly to a device that is adapted to prevent a backfirefrom traveling upstream in a pipe or conduit through which an explosivemixture of gas and air is traveling. Devices of this type are commonlyknown as firechecks.

Devices of the type with which this invention is concerned are in wideuse with industrial heating equipment, and one is shown, for example, inHess Patent 2,332,380. The fire check shown in that patent, as well asothers with which the applicant is familiar, have the disadvantage thatthey are diflicult and costly to manufacture, assemble and adjust foroperation. Many of them are also difficult to reset after a backfire hastaken place.

It is an object of the invention to provide a firecheck which isinexpensive to manufacture, and which is easy to assemble. It is afurther object of the invention to provide a firecheck in which all ofthe movable parts are aligned and move along a single axis. It is alsoanobject of the invention to provide a fire check that is operative,-without adjustment, when placed in any position in a fuel line.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, its advantages and specific objects attained with its use,reference should be had to the accompanying drawings and descriptivematter in which I have illustrated and described a preferred embodimentof the invention.

In the drawings: I

Fig. 1 is a section through the apparatus, I I

Fig. 2 is a top view of a portion of the apparatus taken on line 2r-2 ofFig. l, i

Fig. 3 is a bottom view of an adjusting member, and

Fig. 4 is a partial view of a portion of the apparatus showing amodification thereof. i

The fire check of the invention is housed in a body formed of a casting1 having an inlet 2 and an outlet 3 that are aligned with each other.The interior of the body is provided with a partition forming a passage4 that is shown herein as being substantially perpendicular to the inletand outlet. The various operative parts of the device are located in orareconcentric with this passage.

The upper end of the partition forming passage 4 is undercut as shown at5 to locate a retaining ring 6. A fire screen 7 is pressed against theother face of the ring.- Screen 7 may be formed in any conventionalway,but is preferably made of a strip of thin corrugated metal that istightly wound around a spool 8. A'fuel' mixture can flow through thepassages formed by the corrugations with only a small pressure drop. Itis noted that a bushing 9 is located in the center of the spool.

Screen 7 is held in place, against ring 6, by a casting 11 whose upperend is received in passage 4. To this end the casting is provided withan upperwedge-shaped atent 2 portion 12 that engages a sl1oulder '13machined in the passage. It will be seen from an inspection of thedrawing that the wedge-shape of the ring 12 forces the screen tightlyinto engagement with ring 6. A pin 14 may be provided in the casting 11to extend between a pair of convolutions of the screen in order toprevent any possible rotation thereof. t is noted that casting 11 isprovided with a plurality of inwardly extending ribs 10 that servesomewhat to support the screen and prevent it from telescoping. Thecasting 11 is provided around its lower edge with a radially extendingflange by means of which it is fastened to casting 1 with bolts. 16.When the bolts are threaded into place the casting and the partsassociated with it will be rigidly fastened in the body 1.

Casting 11 is provided with a cylindrical passage 17 that is axiallyaligned with passage 4 in the body 1. The upper end of that portion ofcasting 11 forming passage 17 is machined to make a valve seat 18 whilethe lower edge of this portion is machined to make a second valve seat19. The opening in the bottom of casting 11 is closed by means of a cap21 which is fastened to the casting by suitable screws 22. This cap isprovided with an opening receiving thereina bushing 23. A rod 24- whichserves a number of purposes to be described below is guided for verticalreciprocating movement in bushings 9 and 23.

The lower end of rod 24 has a collar 25 on it, the

upper surface of which is formed as a spherical seat 26. Resting looselyon this seat, and surrounding the rod, is a valve 27 that is adapted toengage valve seat 19 of casting 11 A pin extends through the rod abovethe valve to prevent the valve from falling into engagement with seat 19if the device is used in an inverted position. Rod 24 is normally biasedin an upwardly direction to move the valve 27 against the valve seat 19by means of a spring 29 that extends between a ledge formed on the innersurface of cap 21 and a disc 23 that is fastened to the rod below collar25. The arrangement just described permits a slight movement of valve 27relative to rod 24 around seat 26 when the valve is closed. Thus anyslight misalignment of the parts is compensated for, and the valve canclose tightly.

Another valve 31, that serves as an automatic check valve, is slidablymounted on rod 24 between passage 17 and screen 7. A light spring 32normally biases this valve toward seat 18 to' close the passage, asshown by the right side of the valve. Valve 31 is made of a lightmaterial such as aluminum and, during operation of the device, is keptopen by gas flowing through passage 17, as shown by the left side of thevalve.

Rod 24 is held in its lower position with valve 27 open, as shown in-Fig. 1 of the drawing, by means of a pair of bimetallic strips 33 thatengage a pair of shoulders 34 formed adjacent to its upper end. The endsof the bimetallic strips 33 bent to U-shape as shown at 35 in Fig. 2 andthey are supported on a pair of ledges 36 that extend inwardly from ring6; The strips are held in position on the ledges by suitable cap screws37.

The lower end of the device is sealed by means of a diaphragm 38 that issuitably held in a conventional manner on rod 24 with the outer edge ofthe diaphragm being fastened between the lower end of cap 21 and acylindrical sleeve 39. Sleeve 39 is held in position by screws 41.

Rod 24 can be moved manually from its upper position in which valve 27is closed to its lower position shown in the drawing by means of anextension 42 that is suitably threaded into the end of the rod. Thisextension is square for a purpose to be described below and passesthrough a suitable square opening in a cup 43 that is held against thelower end ofsleeve 39 by screws 44. It is noted, as' best shown in Fig.3, that this cup is provided with a pair of arcuate slots 45 throughwhich the screws extend.

In the operation of the apparatus, with the parts in the position shownin Fig. l, a combustible mixture of gas and air is supplied to the inlet2. This mixture will pass through passage 17 of casting 11 and passage 4of the body 1 to outlet 3. In the normal course of events, the flow ofthe fuel mixture will be unrestricted except by the small pressure dropwhich occurs as the mixture passes valve 31 and through the intersticesof screen 7. If, however, there should be a backfire from the burners,or other apparatus that is being supplied with the combustible mixture,a pressure wave will travel back through the outlet into body 1 andthrough screen 7. This pressure wave will be greater than the normalpressure of the mixture and will therefore permit valve 31 to movedownwardly along rod 24 and close off the supply of the fuel so thatthis pressure wave cannot be transmitted through the device to thesource of supply.

Occasionally a backfire is accompanied by travel of the flame front backinto body 1. When this takes place screen 7 will prevent travel of theflame front beyond this point. Even if the increased pressure resultingfrom the backfire is terminated, and valve 31 opens so gas can stillfiow through the screen, the gas will burn along the upper face thereof.As this burning takes place, the bimetallic strips 33 will be heated andwill warp outwardly as shown by the dotted lines in Fig. 2, therebymoving the strips ofl shoulders 34 formed on rod 24. When the bimetallicstrips have been heated sufiiciently to free rod 24, spring 29 willforce the rod upwardly, thereby closing valve 27 to cut otf the supplyof fuel. The valve will be retained in its closed position by spring 29until such time as it is opened manually. After the cause of thebackfire has been corrected and strips 33 have cooled enough to returnto their full line position in Fig. 2, an attendant will grasp extension42 and move it downwardly. Thereupon the bimetallic strips will snapover shoulders 34 to hold the rod in its lower position with valve 27open, and the apparatus again will be in operative condition.

From time to time it may be desirable to test the apparatus, and also tomove rod 24 to clear it of any dirt or the like which may have beendeposited thereon by the fuel mixture flowing through the device. Thiscan be accomplished by loosening screws 44, and rotating cup 43. Whenthe cup has been rotated through substantially 90, rod 24 will have beenrotated to a position so that the shoulders 34 will no longer beefiective to block movement of the rod. Rod 24 can be moved, when it isin this position, both manually and by spring 29 to test itsoperativeness. Rotating the cup back to the position shown in Fig. 3 ofthe drawing will return shoulders 34 to a position under the edges ofbimetallic strips 33 and thereby again place the device in operativecondition.

It will be seen from an inspection of the drawing that all of theoperative parts of the device are concentrically located and are in astraight line. This construction makes the assembly of the device easilyaccomplished and also makes its manufacture easy because of thearrangement of the machined surfaces of the body and casting 11. Theaxial alignment of the various parts insures that the fuel mixture willtravel through a minimum of restrictions as it is going from the inletto the outlet of the device, and thereby reduce the pressure drop whichis normally occasioned by the flow of such a gas.

For some applications it may be desirable to have an indication when abackfire has occurred which causes valve 27 to close. This can beaccomplished by using movement of rod 24 to actuate an electric sw tchthat is in an indicating circuit. To this end the cylindrical member 39,as shown in Fig. 4, can be modified to support an electric switch 46 ofa standard type. This switch is provided with a plunger 47 that isactuated by a cam portion 48 formed on the extension 42 of rod 24. Whenthe rod moves upwardly due to heating of bimetallic strips 33, the rodwill be moved from the position shown in Fig. 1 to that shown in Fig. 4.During this movement the plunger 47 of the switch will move to the leftin Fig. 4 to actuate the switch. As extension 42 is moved downwardly inFig. 4 to reset the device, plunger 47 will be moved to the right toreset the switch and the control circuit actuated thereby.

From the above it will be seen that I have invented an automatic firecheck that is inexpensive to manufacture and is readily assembled. Whenrepair or replacement of any of the parts is required, they can all bereached from a single location. The device can be placed in a straightpipe line with a minimum of inconvenience, and it is operative, withoutadjustment of the parts, when located in any position.

While in accordance with the provisions of the statutes, I haveillustrated and described the best form of embodiment of my inventionnow known to me, it will be apparent to those skilled in the art thatchanges may be made in the form of the apparatus disclosed withoutdeparting from the spirit and scope of the invention as set forth in theappended claims, and that in some cases certain features of my inventionmay be used to advantage without a corresponding use of other features.

What is claimed is:

1. A firecheck including a body having a straight passage through whicha fuel mixture flows, said passage being provided along its length witha partition having formed thereon a pair of annular and opposed valveseats, a screen across said passage downstream of said valve seats, arod extending axially of said passage through said screenand valveseats, a first valve being slidable on said rod between said partitionand screen and being biased in one direction toward the one of saidvalve seats facing said screen and being adapted to be opened by flow ofmixture through said passage, a second valve on said rod and movabletherewith, means to bias said rod in the opposite direction to move saidsecond valve against the other of said pair of valve seats, andtemperature responsive means downstream of said screen to hold said rodin valve open position.

2. The combination of claim 1 in which said rod is provided with anenlargement having a substantially spherical bearing surface formedthereon and said second valve is provided with a seat engaging saidsurface whereby said second valve can be tilted relative to said rod asit engages said other valve seat.

3. A fire check comprising a body having an inlet and an outlet,partition means between said inlet and outlet having a passage thereinwith an axis and through which a fuel mixture flows and a pair ofaxially displaced valve seats, one on each side of said partition,concentric with said axis, a screen located across said passagedownstream of said partition, a rod, means in said screen and said bodyto mount said rod for reciprocating movement along the axis of saidpassage, a first valve slidable on said rod between said partition andscreen, means to bias said first valve in one direction toward closedposition against said valve seat on the side of said partition towardsaid screen, said first valve being opened by flow of mixture throughsaid passage, a second valve on said rod, means to bias said rod in theopposite direction to close said second valve against the other valveseat,

and temperature responsive means to hold said rod in a position tomaintain said second valve open.

4. In a fire check, a casing having an aligned inlet and outlet for afuel mixture, means forming a passage in said body between said inletand outlet at an angle thereto, a screen across said passage adjacent tothe outlet end thereof, said passage being provided with means forming apair of aligned valve seats upstream of said screen, a first valvealigned with said with said screen and adapted to engage the valve seatnearest said screen to close said passage, means biasing said firstvalve in a closed direction against the flow of mixture, a second valvealigned with said first valve and adapted to engage the other valve seatto close said passage, means biasing said second valve toward closedposition, temperature responsive means across said passage downstream ofsaid screen, and means controlled by said temperature responsive meansto hold said second valve in open position.

5. In a firecheck, a body having an inlet and an outlet, said body beingprovided with a passage therein between said inlet and outlet, saidpassage having a shoulder extending radially inward around one edgethereof, a screen received in said passage and located by said shoulder,means received in said passage and abutting said screen and including aportion forming a partition between said inlet and outlet upstream ofsaid screen, said portion being provided with an opening concentric withsaid passage, opposite edges of said opening forming valve seats, a rodconcentric with said passage and said opening, a first valve betweensaid screen and opening slidable on said rod adapted to engage the valveseat facing said screen and moved to open position by flow of gas fromsaid inlet to said outlet through said opening, a second valve attachedto said rod operable to engage said other valve seat, and means to biassaid rod in a valve closing direction.

6. In a fire check, a hollow body provided with an axially aligned inletand outlet, with a passage between the two having an axis at an angle tosaid inlet and outlet and an opening in said body aligned with saidpassage, said body having a flange extending radially inward around saidpassage at the end thereof remote from said opening, a screen placed insaid passage through said opening and abutting said flange, partitionmeans placed in said body through said opening and engaging said screen,said partition being provided with a passage therein aligned with thepassage in said body, the passage in said partition being provided witha valve seat at each end thereof, a rod extending through said screenand said opening, a first valve between said screen and opening engagingthe valve seat facing said screen and slidable on said rod, means tobias said valve to closed position, said valve being opened by a flow ofgas through said passage, a second valve to engage the other valve seatfixed to said rod, means to bias said rod in valve closing direction, acover for said opening, said cover having means therein to guide saidrod, and means normally to hold said rod in a position in which saidsecond valve is away from its valve seat.

References Cited in the file of this patent UNITED STATES PATENTS HessOct. 19, 1943

1. A FIRECHECK INCLUDING A BODY HAVING A STRAIGHT PASSAGE THROUGH WHICHA FUEL MIXING FLOWS, SAID PASSAGE BEING PROVIDED ALONG ITS LENGTH WITH APARTITION HAVING FORMED THEREON A PAIR OF ANNULAR AND OPPOSED VALVESSEATS, A SCREEN ACROSS SAID PASSAGE DOWNSTREAM OF SAID VALVE SEATS, AROD EXTENDING AXIALLY OF SAID PASSAGE THROUGH SAID SCREEN AND VALVESEATS, A FIRST VALVE BEING SLIDABLE ON SAID ROD BETWEEN SAID PARTITIONAND SCREEN AND BEING BIASED IN ONE DIRECTION TOWARD THE ONE OF SAIDVALVE SEATS FACING SAID SCREEN AND BEING ADAPTED TO BE OPENED BY FLOW OFMIXTURE THROUGH SAID PASSAGE, A SECOND VALVE ON SAID ROD AND MOVABLETHEREWITH, MEANS TO BIAS SAID ROD IN THE OPPOSITE DIRECTION TO MOVE SAIDSECOND VALVE AGAINST THE OTHER OF SAID PAIR OF VALVE SEATS, ANDTEMPERATURE RESPONSIVE MEANS DOWNSTREAM OF SAID SCREEN TO HOLD SAID RODIN VALVE OPEN POSITION.